The present invention is directed to approaches to increase the performance of fiber reinforced polymers under aging conditions including the use of oil-in-water emulsions of antioxidants that are water insoluble or immiscible or have limited water solubility, wherein the emulsions have a small particle size and good stability.
More particularly, the present invention is directed to methods and compositions for increasing the performance of glass fiber reinforced polymers under thermal aging conditions. The compositions include the use of oil-in-water emulsions of antioxidants that are water insoluble or immiscible or have limited water solubility and that are of low volatility and good thermal stability and non-discoloring for use in treating glass fibers. The oil-in-water emulsion provides a method to reduce chemical degradation of polymers reinforced with glass fibers containing sizing compositions.
In order to stabilize polymers from degradation due to oxygen and ozone, various antioxidants of the hindered phenol and diaryl amines types have been incorporated into polymer formulations. Another type of degradation that polymers may encounter is degradation due to various chemicals other than oxygen and ozone with which the polymers may come in contact. Such chemical degradation may occur when the polymers are reinforced with material that has been treated with various chemicals to provide efficient processing of the materials and to provide compatibilty of the materials with the polymers. Care must be taken in producing reinforcement materials containing treatment chemicals, such as sizing compositions for glass fibers, to avoid any problem of interaction between the chemistry on the reinforcing material and the polymers. Any possible interaction between the various chemical agents in the system or reaction or decomposition products of these chemical agents with the polymer may degrade the polymer to some degree. This degradation would reduce the mechanical properties of the reinforced polymer over time and especially under thermal aging conditions. When the reinforced polymer is subjected to elevated temperatures for a period of time, i.e., thermal aging, degradation of the polymer may be accelerated due to thermal autooxidation and increased reaction rates for chemical interaction. This degradation shortens the useful properties of the reinforced polymer which usually have extended properties due to the presence of the reinforcement.
Antioxidants that have been added to polymer compositions that are to be used in preparing reinforced polymers have also been added in the form of the antioxidant alone as a solid or liquid. Also, antioxidants have been added to latex formulations such as rubber latices in the form of emulsion and dispersions. For example, the antioxidant "Age Rite Resin D" available from R. T. Vanderbilt Company, Inc. which is the antioxidant polymerized 1,2-dihydro-2,2,4-trimethyl quinoline can be prepared in a 30% emulsion by melting the "Age Rite Resin D" antioxidant in light process oil and oleic acid at 104.degree. C. and removing the mixture from the heating source and adding xylol. Then the emulsifier nonylphenoxy poly(ethyleneoxy)ethanol available from GAF Corporation Chemical Products under the trade designation "Igepal CO-630" is diluted. Dissolved potassium hydroxide pellets are mixed with the emulsifier and the mixture is heated to about 88.degree. C. The emulsifier mix is then added to the antioxidant mix with vigorous agitation to produce an emulsion having about 32.1 percent oil to 31.8 percent water. Other similar emulsions and dispersions are available in the publication "Vanderbilt News" volume 34, number 2, 1972, pp 13-24.
An emulsion is a two phase system consisting of two incompletely miscible liquids, the one being dispersed as fine droplets in the other, whereas a suspension is a two phase system where the dispersed phase is a solid. As stated above both emulsions and dispersions of antioxidants have been used in formulations for rubber latices. The stability of antioxidant emulsions depends upon the factors for emulsions in general: (1) particle size, (2) difference between the densities of the material in the internal phase, which is the liquid broken into droplets and of the material in the external phase, which is the surrounding material, (3) the viscosity of the emulsion concentrate, (4) the charges on the particles, (5) choice of emulsifier type and amount of emulsifier used, and (6) the conditions of storage such as agitation, temperature, dilution, and evaporation.
Additional applications of antioxidant emulsions may be developed if the emulsions have a small average particle size of around 1.5 microns and a sufficiently narrow particle size distribution. Such additional application can be found in the coating industry where coating or treating solutions for various materials would benefit from a small average particle size, fairly narrow particle size distribution antioxidant emulsion. Antioxidants that would be particularly useful in a small average particle size, fairly narrow particle size distribution emulsion would be those that are of low volatility, and/or heat resistant and/or nondiscoloring.
It is an object of the present invention to provide an oil-in-water emulsion of an antioxidant and especially antioxidants of low volatility, and/or heat resistant, and/or non-discoloring that has an average particle size of less than 1.5 microns, a fairly narrow particle size distribution, good stability and good dilutability to a low concentration.
It is an additional object of the present invention to provide a treating composition for glass fibers that are to be used for reinforcement of various polymeric materials and that reduce degradation of the reinforced polymer due to an interaction between the chemicals in the treating composition or their reaction or decomposition products and the polymeric material.
It is a further additional object of the present invention to provide a method for reducing degradation of a glass fiber reinforced polymer due to any interaction between the materials present in the sized glass fiber strand and/or reaction or thermal decomposition products thereof under thermal aging conditions, thereby reducing any decrease in mechanical properties of the reinforced polymer due to such degradation.